Catalyst is a chemical substance for improving chemical reaction occurrences or the reaction rate due to that the reduction of the energy (activation energy) for chemical reactions without changing itself. For nano-materials speaking, each size of which is roughly between 1 to 100 nm. They provide special properties that general materials do not, such as light absorption, catalytic and other characteristics, for many prospect applications due to the small-sized, large specific surface area, catalytic and quantum-sized effect. In recent years, metallic nano-particles become one of the most popular research topics since they are critical elements in catalyst applications due to the large specific surface area and novel catalytic property. A further step for the practical application is that the bi-metallic nano-particles can improve their catalytic performances by varying their compositions and atomic configurations.
Platinum is used as a cathode catalyst in membrane fuel cells for improving the oxygen or air reduction reactions, and the platinum alloy is used as an anode catalyst in membrane fuel cells for improving the fuel (hydrogen and methanol aqueous solutions) oxidation reactions. The purpose of using platinum alloy as the anodic catalyst is to avoid them from the poisoning of intermediates of carbon monoxide or other methanol oxidation species at low temperature (lower than 100° C.) environment. This is one of the key technologies of membrane fuel cells. Bi-metallic alloy, such as platinum-ruthenium (Pt—Ru) alloy, is the most widely used as the anode catalyst, and other multi-metal alloys, such as Pt—Ru—Rh and Pt—Ru—Rh—Ir is currently researched and developed and expected with better catalyst efficiency and anti-poisoning ability than the bi-metallic Pt—Ru alloy. In catalyst production, besides the well situated grain size and dispersion, the platinum alloy catalyst must have appropriate composition, such as Pt—Ru with Pt:Ru around 1:1 ratio of the number of atoms, for improving their catalytic properties.
In general, due to the benefit of low cost, light weight, and as the carrier and conducting materials for electrodes or membrane electrode assembly (MEA) production, the carbon black powder (such as Vulcan XC72 produced by Cabot Corporation, United States) is widely used as the main carrier for the production of platinum alloy catalyst. However, using Platinum based electrochemical catalysts in general membrane fuel cells or solar cells are not yet perfected due to the low energy conversion efficiency and high fabrication cost. Therefore, it is an important and meaningful issue that to improve the performance of catalysts used in proton membrane fuel cells, solar cells and other applications without the need to increase the loaded amounts of noble metal and most importantly to improve the overall performance of the device.